Hi Natalie,
The choice of having a 3 or 4 bottle routine is very much up to you and your lo - some parents have found that their los prefer 4 smaller milkfeeds, others 3 larger ones, isn't really that important - what matters is that your lo prioritises milk over solid foods because that's what he needs from a nutritional perspective!
I'll direct you to this FAQ babywhispererforums.com/index.php?topic=118497.0 which answers some of your questions about the milk/solid order, and how to fit food into EASY - I would suggest that you could offer ds more milk at each of the 4 feeds (20oz is a minimum recommended amount, it would be preferable for him to still be on his pre-solids quantity of milk until at least 9 months).
HTH?
Ax